Longest XOR path (dfs+01trie)

The longest XOR path - Luogu https://www.luogu.com.cn/problem/P4551 First use dfs Node 1 Find the XOR path value to all points , According to the XOR property, the XOR distance between any two points can be obtained , In this case, the problem is to find the maximum XOR distance between two points , It can be transformed into finding the maximum XOR value of a sequence for a number , You can use it 01trie To write the

#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <map>
#include <queue>
#define lowbit(x) ((x)&(-x))
using namespace std;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
using pll=pair<ll,ll>;
const int MAXN=1e6+5;
const int INF=0x3f3f3f3f;
const ll NNF=0x3f3f3f3f3f3f3f3f;
const int MAXBIT=31;

int n;
int head[MAXN];
int ver[MAXN];
int cost[MAXN];
int num[MAXN];
int nxt[MAXN];
int tri[MAXN][2];
int rec=1;
int cnt;
void add(int x,int y,int c){
	ver[++cnt]=y;
	cost[cnt]=c;
	nxt[cnt]=head[x];
	head[x]=cnt;
}
int d[MAXN];
void dfs(int p,int fa){
//	printf("===\n");
	for(int i=head[p];i;i=nxt[i]){
		int v=ver[i];
		if(v==fa) continue;
		d[v]=d[p]^cost[i];
		dfs(v,p);
	}
}

void insert(int x){
	int cur=1;
	for(int i=MAXBIT;i>=0;i--){
		int bit=x>>i&1;
		if(!tri[cur][bit]) tri[cur][bit]=++rec;
		cur=tri[cur][bit];
	}
	num[cur]=x;
}

int find_max(int x){
	int cur=1;
	for(int i=MAXBIT;i>=0;i--){
		int bit=x>>i&1;
		if(tri[cur][bit^1]) cur=tri[cur][bit^1];
		else cur=tri[cur][bit];
	}
	return x^num[cur];
}

int main(){
	scanf("%d",&n);
	int x,y,c;
	for(int i=1;i<n;i++){
		scanf("%d %d %d",&x,&y,&c);
		add(x,y,c);
		add(y,x,c);
	}
	dfs(1,-1);
	for(int i=1;i<=n;i++){
		insert(d[i]);
	}
	int mx=0;
	for(int i=1;i<=n;i++){
		mx=max(mx,find_max(d[i]));
	}
	printf("%d",mx);
	return 0;
}